I just downloaded the 4.3.4 firmware, is it possible to change back to 4.3.3? (ITOUCH 4G)?

You need to have your shsh blobs saved to beable to downgrade past 4.3.4 (or 4.0.2, but ipod touch 4g's dont have to worry about about that, because 4.1 is the farthest you can go). So apple has officially made you f***ed. Shouldve done your research first. If i were you, start saving your shsh blobs now, because if apple makes another one of those lockpoints, you be stuck with them. I upgraded to 4.2.1, and it made my ipod touch 2g slow, so i wish i couldve restored back to 3.1.3 (even though i hate old versions, but it wouldve made it faster without airplay, gamecenter, spotlight, and a bunch of other stuff).

Here is a video showing you how to save your blobs EASILY! (one click of the mouse):

http://www.youtube.com/watch?v=5PbtN5pOUwE

if you have your shsh blobs saved then yes you can

if not then no

You cannot downgrade

not possible... sorry.